The present invention relates to a process and apparatus for manufacturing sewn books.
As is known, books are made of a plurality of signatures joined together, and can be divided into sewn books and what are termed "perfect bound" books, called "paper-backs" though they may have hard covers.
In order to obtain a sewn book, a book-binding operation is carried out. The signatures for each individual book are grouped together in the correct order on a gathering machine and the groups are delivered to thread sewers for sewing the individual signatures together.
At present, a gathering machine has an average rate of delivery of about 3,000 books per hour, in theory almost independent of the number of signatures in the book.
In turn, a sewer, even if it is fed automatically by a feeder, cannot sew more than 5,000 signatures per hour, giving, for an average book of 20 signatures, a rate of production of 5,000 + 20 = 250 books per hour.
Thus to deal with the output of one gathering machine, one requires 3,000 + 250 = 12 automatic sewers controlled by a corresponding number of operators. In addition, there is no continuity of operation between the one gathering machine and the sewers which are necessary to cope with the output of the gathering machine. The groups of signatures formed by the gathering machine must be stored before passing them to the sewers in a second phase.
As a result, space and equipment must be provided for storing the groups of signatures delivered by the gathering machine, and manual operations and equipment are required for delivering the groups to the sewers. This causes a notable increase in production costs.
For forming perfect bound books, the signatures are gathered on a gathering machine, as in the case above, and the groups of signatures then pass directly, by way of a short conveyor, to a so-called "perfect" binder. The perfect binder has different work stations in which the back of each group of signatures is milled to ensure that the book is formed on a number of single sheets, and a layer of adhesive is applied to the back of the book to join the single sheets together. The perfect binder also carries out same further operations for finishing the book.
A perfect binder works at substantially the same rate as the gathering machine, that is to say, 12 times as fast as a sewer.
The quality of the books manufactured by the two different methods is however very different. The quality of perfect bound books is low, and the difficulty in opening the book and the low strength of the join between the sheets in general limit the method of manufacture to low-price books which are read just once or only a few times. On the other hand, the quality of sewn books is high. Sewing, although expensive, is used for valuable books and for all books intended to be subjected to considerable use, for example school books, and the method is widely used.